final examination chemistry 3b name: sid #: laboratory gsi

1

FINAL EXAMINATION Chemistry 3B

Name:__________________________ SID #:______________________ Print first name before second! Use capital letters!

Laboratory GSI (if applicable): Peter Vollhardt ______________________ December 15, 2006 Please provide the following information if applicable. Making up an I Grade _____ (If you are, please indicate the semester during which you took previous Chem 3B: �–�–�–�–�–�–�–�–�–�–�–�–�–�–�– �–�–�–�–�–�–�–�–�–�–�–�– Semester Instructor Please write the answer you wish to be graded in the spaces provided. Do scratch work on the back of the pages. This test should have 25 numbered pages. Check to make sure that you have received a complete exam. A good piece of advice: Read carefully over the questions (at least twice); make sure that you understand exactly what is being asked; avoid sloppy structures or phrases. It is better to be pedantic in accuracy now than sorry later! Grades will be posted on Wednesday, December 20, by 5 pm, outside 320 Latimer Hall. Good Luck! DO NOT WRITE IN THIS SPACE

I. ______ (60)

II. ______ (175)

III. ______ (60)

IV. ______ (40)

V. ______ (60)

VI. ______ (60)

VII. ______ (45)

Total:

(500)

2

I. [60 Points] Provide the IUPAC name or draw the structure, as appropriate, of the following

molecules. Remember the priority of functional groups in choosing names, indicate the correct stereochemistry (e.g., R, S, and E, Z), and do not forget about the alphabetical ordering of substituents!

(a)

(2S)-Amino-6-heptynoic acid

(b)

ClCl

Br

(c)

(R)-2, 3-Dihydroxypropanal

3

(d)

OCH2CH3

OO

(e)

N-(2-Methylpropyl)ethanamide

(f)

O

4

II. [175 Points; (a) - (j) 10 points each, (k) - (o) 15 points each] Add the missing components (starting materials, reagents, or products) of the following reactions in the boxes provided. Aqueous work-up (when required) is assumed to be part of a step. It is not part of any answer.

(a)

OS

CH3

OO

Na+-OCH3, CH3OH

(b) 1.

2.

NH2

O

OCH3

CH3 CH3O

OCH3

H

H(c)

5

(d)

P2S5

O

O

1H NMR: =2.35 (s, 6H), 2.01 (s, 6H) ppm (e)

N

CH3

HNO3, H+

(f)

O

H

HO

H

HO

HO

H

HHOH

OH

CH3OH, H+

(g)

O

CH3NH2, Na+ NCBH3�–

6

(h) +

CN

(i) 13C NMR = 220.2, 38.3, 23.3 ppm (j) Na+�–OCH3, HCH3OH

1H NMR spectrum:

CH3COOH

O

O

O

OCH3

O O

7

(k) 1.

NH

O 2. 3.

+N N

(l) 1. 2. 3COCH3

O

CH3CHCH2COCH3

OH O

CH

(m) 1. CH3OH, H+

2. 2 CH3MgBr

H+, CH3OH

OH

O

8

(n) 1. NaCN

2. CH3CH2CH2MgBr 3. CH2=P(C6H5)3

CH3I Mass spectrum of product: (o)

OCH3

O O

+

NH

OCH3CH3O

H3C CH3

O O +

9

III. [60 Points] In an attempt to effect electrophilic methoxylation, benzene carbaldehyde A was treated with methyl hydroperoxide B in the presence of acid. The mass, IR, and NMR spectra of this product are shown in the following pages. From the complex mixture of products, traces of unknown C were obtained. H+

C (Unknown) + CH3OOH

H

O

A B

(a) After consideration of the spectral data, write the structure of the product in the box below. Structure of unknown

b. Interpret the spectral data as requested in the spaces provided, starting on the following page.

10

1. 1H NMR Spectrum (for expanded section, see bottom spectrum).

11

b. Draw again your suggestion for the unknown in the box and label the hydrogens A, B, C, and D giving rise to the corresponding signals in the spectrum. Use the Table below, if necessary. 2. 13C NMR Spectrum.

12

Draw again your suggestion for the unknown in the box below and label the types of carbon atoms A�–E giving rise to the corresponding signals in the spectrum. 3. Mass spectrum.

13

a. Clearly mark on the spectrum the molecular ion as �“M+�”. b. In the boxes above the respective fragment ions, indicate the molecular piece that has fragmented from M+, e.g. �“Cl�”, or �“CH3O�”, or �“CH3CH2�”, or ? 4. IR Spectrum.

14

Confirm or rule out the presence or absence (circle one) of the following bonds. Enter an approximate expected stretching frequency in the box. ~ (Csp

2�–H) is: present absent at cm�–1

~ (Csp


~ (O�–H) is: present absent at cm�–1

~ (C=O) is: present absent at

cm�–1

15

IV. [40 Points] You are asked to assign the structures of the two pentoses D-ribose and D-lyxose. Ruff degradation of the former gives D-erythrose, that of the latter D-threose. Kiliani-Fischer extension of D-ribose furnishes D-allose and D-altrose, that of D-lyxose results in D-galactose and D-talose ribose. CHO CHO

HO H

CH2OH

H OH

H OH

CH2OH

H OH

D-(-)-Erythrose D-(-)-Threose D-Ribose D-Lyxose CHO

OHH

OHH

OHH

OHH

CH2OH

CHO

HHO

OHH

OHH

OHH

CH2OH

CHO

OHH

HHO

HHO

OHH

CH2OH

CHO

HHO

HHO

HHO

OHH

CH2OH

D-Allose D-Altrose D-Galactose D-Talose 1. Draw your assignments in the respective boxes, using Fischer projections.

16

2. Specify the conditions of (a) the Ruff degradation

1. 2.

(b) the Kiliani-Fischer extension

1. 2.

17

V. [60 Points] Write detailed step-wise mechanisms for the following transformations. Use only structures and �“arrow-pushing�” techniques. Note: These are not synthetic problems. Do not add any reagents! What you see is what you have! Work from left to right in the following spaces. There is much more space than you will need. (a)

NaOH,

OH

OH

O

18

(b) 1. LiAlD4 2. H+, H2O (work up)

O

ON

CH3

N

O

OH

CH3

CH2D

Work from left to right in the following spaces. There is much more space than you will

need.

19

(c) NaBH3CN, CH3OH 2N

H

O

NH

H

Work from left to right in the following spaces. There is much more space than you will need.

20

VI. [60 Points] Provide a reasonable synthetic route from starting materials to product. Note: Several steps are required, and there may be more than one solution to the problem. You may use any additional organic or organometallic reagents to effect your conversions. Do not write mechanisms!

(a)

N O

O

H


21

(b) H2N CNH

O

COOH

H2N COOH

22

(c) The only organic starting materials:

OCH3

O O OCH3

N NO

O

O


23

VII. [45 Points] Place an X mark in the box next to the most accurate statement.

(a) The longest wavelength band in the UV spectra of the hydrocarbons below moves to lower energy in the order

1 2 3 1, 2, 3

3, 2, 1

2, 1, 3

3, 1, 2

(b) Circle the compounds which are aromatic

O2N H

+N

N

O

N

NH

O

O

24

(c) In the collection below, circle the most abundant fragments formed during the mass spectral ionization of 2-pentanone.

O

70 eV H+ C O CH3+ CH3CH

2

+ CH 2

+3CH2CH C3H6O+ C2H4

+

(d) The rates of electrophilic aromatic nitration of the following compounds increases in the order

Cl

Cl

N NCH3

1 2 3

1, 2, 3

2, 1, 3,

3, 2, 1

2, 3, 1

25

(e) Give the products and their molar amounts per mole of starting material of the complete periodic acid oxidation of D-erythrose and D-erythrulose.

CHO

OHH

OHH

CH2OH

HIO4 D-Erythrose

CH2OH

O

OHH

CH2OH

D-Erythrulose

The End

Merry Christmas!

1



Laboratory GSI (if applicable): Peter Vollhardt ______________________ December 17, 2008 Please provide the following information if applicable. Making up an I Grade _____ (If you are, please indicate the semester during which you took previous Chem 3B: �–�–�–�–�–�–�–�–�–�–�–�–�–�–�– �–�–�–�–�–�–�–�–�–�–�–�– Semester Instructor Please write the answer you wish to be graded in the spaces provided. Do scratch work on the back of the pages. This test should have 25 numbered pages. Check to make sure that you have received a complete exam. A good piece of advice: Read carefully over the questions (at least twice); make sure that you understand exactly what is being asked; avoid sloppy structures or phrases. It is better to be pedantic in accuracy now than sorry later! Good Luck! DO NOT WRITE IN THIS SPACE

I. ______ (60)

II. ______ (175)

III. ______ (60)

IV. ______ (40)

V. ______ (60)

VI. ______ (60)

VII. ______ (45)

Total:

(500)

2

I. [60 Points] Provide the IUPAC name or draw the structure, as appropriate, of the following

molecules. Remember the priority of functional groups in choosing names and indicate the correct stereochemistry (cis, trans, E, Z, R, and S, as appropriate)!

(a) Trans-3-oxo-4-hexenal

(b) 1-Bromo-4-(2,2-dichloropropyl)benzene

(c) (R)-2,3-Dihydroxypropanenitrile

1

2

3

(Fischer projection)

The numbers refer to the main chain

3

(d)

OCH2CH3

OH2N H

(e) N-Chloro-N-methyl-3-pentanamine

(f)

O

4


(a)

OS

CH3

OO

+CH3OH

O

O

O

O

Na+

(b) 1.

2.

NH2

H3CO

OCH3

H3CO

CH3O

OCH3

H3CO I

(c)

H

H

5

(d)

O

O

NH3, H+

13C NMR spectrum:

(e)

H3CN

HNO3, H+

NH2 (f)

O

H

H3CO

H

H3CO

H3CO

H

HHOCH3

OCH3

H2O, H+

mildly acidic O

6

(g) Two reagents

NH CH3

O

(h)

+

CN

H3CO

CN

(i) + NaOH

H2N ONH2

7

(j) OH

H3CO

1. LiAlH4 2. H+, H2O

IR spectrum of starting material:

13C NMR spectrum of starting material:

8

(k) 1. 2.

H3C OH O (l) 1. 2. 3.

OH

NH2

NH2

Br

(m) HIO4

2 HCOOH + 1 CH2=O An aldose

9

(n) 2.

CH3

1. N Br

O

O

Mass spectrum of product: 1H NMR spectrum of product:

ppm (o) 1. MnO2 2. NH3 + 3.

COOH

NH2

OH

10

III. [60 Points] Diethyl malonate A was treated with bromine to give a product B. The mass, IR, and NMR spectra of B are shown in the following pages in the sequence :

1. 1H NMR , 2. 13C NMR , 3. Mass , 4. IR. B

Br2

OO

OO

A

(a) After consideration of the spectral data, write the structure of B in the box below. Structure of B

11

1. 1H NMR spectrum (for expanded sections, see bottom spectra).

ppm

A

B

C

C (B

A

J = 8 Hz) (J = 8 Hz)

ppm ppm

12

b. Draw again your suggestion for B in the box and label the hydrogens A, B, and C giving rise to the corresponding signals in the 1H NMR spectrum. Use the Table below, if necessary.

13

2. 13C NMR spectrum.

A

B

C

D

14

Draw again your suggestion for B in the box below and label the types of carbon atoms A�–D giving rise to the corresponding signals in the spectrum. 3. Mass spectrum. Hint: Atomic weights: C = 12; H = 1; O = 16; Br exists in nature as a 1:1 mixture of Br = 79 and Br = 81.

a. Clearly mark on the spectrum the molecular ion(s) �“M+�”. b. In the boxes below, indicate the structure of the fragment ions with the m/z value given under the box. m/z = 193/195 29

15

4. IR Spectrum.

Confirm the presence or absence (circle one) of the following bonds. Enter an approximate expected stretching frequency in the box. ~ (Csp


~ (Csp


~ (O�–H) is: present absent at

cm�–1

~ (C=O) is: present absent at

cm�–1

16

IV. [40 Points] (a) D-Ribulose is a non-reducing pentose. Treatment with NaBH4 gives two alditols. One of them is identical to the product of NaBH4 reduction of D-ribose, the other is identical to the product of NaBH4 reduction of D-arabinose. Fill in the blanks below and provide a structure for D-ribulose. NaBH4

An alditol An alditol D-Ribulose NaBH4 NaBH4 CHO

HHO

OHH

OHH

CH2OHD-Arabinose

OHH

OHH

OHH

CH2OH

CHO

D-Ribose

(b) D-Erythrose was treated with aqueous bromine to give the aldonic acid A, which was

subsequently thermally dehydrated to B, and then treated with acidic acetone to give the final product C. Provide structures for A and B. CHO

H OH

CH2OH

H OH

Br2, H2O

H2O

H2O

OH

OH

C

CH2

O

OCH3

CH3Note: These"corners" are not atoms.

D-Erythrose A B

C

H+, H3C CH3

O

17

V. [60 Points] Write detailed step-wise mechanisms for the following transformations. Use only structures and �“arrow-pushing�” techniques. Note: These are not synthetic problems. Do not add any reagents! What you see is what you have! Work from left to right in the following spaces. There is much more space than you will need. (a)

CH3

O

NaOH, H2O,

H3C

O

+

O

CH3

18

(b)

NO2

O2N

O

2 NaOH, H2O NO2

O2N

Br

O

O


19

(c)

OH

CH3

CH3

H+, H2O

O

H3C CH3 Work from left to right in the following spaces. There is much more space than you will

need.

20

VI. [60 Points] Provide a reasonable synthetic route from starting material to product. Note: Several steps are required, and there may be more than one solution to the problem. Do not write mechanisms! Write out each step separately, including reagents and products. You need to apply retrosynthesis! You may use any additional organic or organometallic reagents to effect your conversions.

(a)

NH2

Note:

HCCl,

O

HCCl,

NH

H2NCCl,

O

and ClCH2NH2 do not exist and are not allowed as reagents.


21

(b)

H2N

O

COOH

NHNH2

COOH

22

(c) For this problem, use the materials given below as the only organic compounds:

IO

O I

O

Starting material

Additional organic reagents


23

VII. [45 Points] Place an X mark in the box next to the most accurate statement. (a) The acidity of 1�–4 increases in the order

H3NCH2COH

O CH3NH3 CH3C N H

1 2 3 4

1, 2, 3, 4

4, 3, 2, 1

4, 1, 2, 3

3, 2, 1, 4

(b) In the 1H NMR spectrum of the compund below circle the hydrogens that you expect to show peaks in the �“left half�” of the spectrum (that is > 5 ppm).

N

NO

OH

H

O

O

H

Cl

H H

H

H

24

(c) The following Diels-Alder reaction follows the endo rule. True or false? Circle the correct answer below

CH3

CO2CH3

CO2CH3

+CO2CH3

CO2CH3

CH3

H

H

True False (d) The mass spectrum of N,N-dipropylpropanamine (see below) shows only a relatively small molecular ion peak at m/z = 143. The base (100%) peak is a fragment at m/z = 114. In the box below the spectrum, draw the structure of this fragment (including charges).

N N,N-dipropylpropanamine

25

(e) Aromatic heterocycles are frequently constructed in one step by a combination of aldol and imine condensations. With this statement in mind provide the most suitable retrosynthetic disconnection of A into two starting materials (boxes).

N CH3

CH3

CH3

O

A

+

The End

Merry Christmas!

1



GSI (if you are taking Chem 3BL): ______________________

Peter Vollhardt December 16, 2009 Please provide the following information if applicable. Making up an I Grade _____ (If you are, please indicate the semester during which you took previous Chem 3B: �–�–�–�–�–�–�–�–�–�–�–�–�–�–�– �–�–�–�–�–�–�–�–�–�–�–�– Semester Instructor Please write the answer you wish to be graded in the spaces provided. Do scratch work on the back of the pages. This test should have 19 numbered pages. Check to make sure that you have received a complete exam. A good piece of advice: Read carefully over the questions (at least twice); make sure that you understand exactly what is being asked; avoid sloppy structures or phrases. It is better to be pedantic in accuracy now than sorry later! Good Luck! DO NOT WRITE IN THIS SPACE

I. ______

(60)

II. ______

(175)

III. ______

(60)

IV. ______

(40)

V. ______

(60)

VI. ______

(60)

VII. ______

(45)

Total:

(500)

2

I. [60 Points] Name or draw, as appropriate, the following molecules according to the

IUPAC rules. Indicate stereochemistry where necessary (cis, trans, E, Z, R, or S). (a) (R)-4-bromo-N-ethyl-N-methyl-pentanamide

(b) 1-Bromo-4-(2,2-dichloropropyl)benzene

(c) (R)-2,3-Dihydroxypropanal

(Fischer projection)

The numbers refer to the main chain

3

(d)

(e) Methyl 3-oxo-butanoate

(f)

4


(a)

H2, Pd�–C

C6H8O (b) 1.

2.

NH2

H3CO

OCH3

H3CO

(c)

H

H

5

(d)

(e)

(f)

(g) H CH3 NaBH3CN, CH3OH H2C=O +

N

6

(h)

OCH3

Complete the stencil above (i)

H3C

O

O

(j)

OH

H3CO

7

(k) 1. 2. (l) 1. 2. 3. (m) HIO4

2 HCOOH + 1 CH2=O An aldose

8

(n) (o) 1. MnO2 2. NH4CN 3. H+, H2O,

OH

9

III. [60 Points] The wavy lines in the following structure indicate four possible retrosynthetic disconnections of four bonds (numbered 1-4). O

1 2 3 4

Show the respective four reactions that would lead to the generation of each of these strategic bonds in the four boxes below. Note: It is fine to use a protected or otherwise modified fragment to make the desired connection, as long as it can be elaborated later into the target structure. However, do not show such elaboration. Each box should contain only the reagents that you would use to make the bond in question. Bond 1: Bond 2: Bond 3: Bond 4:

10

IV. [40 Points] (a) D-Ribulose is a pentaketose. Treatment with NaBH4 gives two alditols. One of them is identical to the product of NaBH4 reduction of D-ribose, the other is identical to the product of NaBH4 reduction of D-arabinose. Fill in the blanks below and provide a structure for D-ribulose. NaBH4

D-Ribulose An alditol An alditol NaBH4 NaBH4

CHO

HHO

OHH

OHH

CH2OHD-Arabinose

OHH

OHH

OHH

CH2OH

CHO

D-Ribose

(b) D-Erythrose was treated with nitric acid to give the aldaric acid A, which was treated

with acidic acetone to give B. On heating, B dehydrated to the final product C. Provide structures for A and B.

11

V. [60 Points] Write detailed step-wise mechanisms for the following transformations. Use only structures and �“arrow-pushing�” techniques. Note: These are not synthetic problems. Do not add any reagents! What you see is what you have! Work from left to right in the following spaces. There is more space than you will need. (a)

H+, H2O, THF

12

(b) H+, H2O


13

(c) H+, H2O,


14

VI. [60 Points] Provide a reasonable synthetic route from starting material to product. Note: Several steps are required, and there may be more than one solution to the problem. Do not write mechanisms! Write out each step separately, including reagents and products. You need to apply retrosynthesis! You may use any additional organic or organometallic reagents to effect your conversions.

(a)


15

(b)

O

NH

S

NH2

S

HOOC


16

(c)


17

VII. [45 Points] Place an X mark in the box next to the most accurate statement. (a) The acidity of 1�–4 increases in the order:

H3NCH2COH

O CH3NH3 CH3C N H

1 2 3 4

1, 2, 3, 4

4, 3, 2, 1

1, 4, 2, 3

3, 2, 1, 4

(b) The following two sugars are:

CHO

OHH

HHO

OHH

OHH

CH2OH CHO

HO H

H OH

HO H

HO H

CH2OH

Identical

Enantiomers

Diastereomers

Anomers

18

(c) The following heterocycle will undergo electrophilic bromination at position:

N

N S

1

23

4

1

2

3

4 (d) The following reaction will give

O

O

Na+ OCH2CH3, CH3CH2OH

O

OO

OH

O

O

OO

19

(e) Which of the following molecules are reduced by LiAlH4? Check all the boxes that apply.

OH

O

N

Cl

The End

Merry Christmas!

final examination chemistry 3b name: sid #: laboratory gsi

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